study of ploidy level of Walnut species and inter-specific hybrids by flow cytometry

In this study, for the first time, the possibility of DNA content and ploidy level of species and inter-specific hybrids of walnut for breeding purposes were examined by flow cytometry. In the spring, the young leaves of samples, including of Persian walnut (J. regia), black walnut (J. nigra), J. hindsii and inter-specific hybrids Paradox (J. hindsii × J. nigra) and Royale (J. hindsii × J. regia) in research station of Karaj, Horticulture Research Department of Seed and Plant improvement Institution were selected, Randomly. DNA content of walnut trees were optimized on the base of tree leaves by method of flow cytometry. In order to comparison and determine the ploidy level, mitotic chromosomes of samples with highest and lowest level of DNA, were counted by using squash method. Ranges of mean or mod of DNA content in samples were different from 46.24 to 71.68. However, the samples had equal (2n=2x=32) chromosomes, so the diversity of DNA index among species were not from changes in the number of chromosomes such as Aneuploidy. The use of flow cytometry as an affordable, easy and rapid method for determination of ploidy level and other tree species is recommended Walnut and the other trees.